SQL : Retrieve first three characters from sql column value - sql

Question

For ex : if sql column value is sa,123k and the output should first three characters i.e. sak
Letters and any special characters needs to be eliminated and gets only three characters. How do we do this ?

Answer 1

You can use recursive CTEs for this purpose:
with t as (
select 'sa,123k' as str
),
cte as (
select str, left(str, 1) as c, stuff(str, 1, 1, '') as rest, 1 as lev,
convert(varchar(max), (case when left(str, 1) like '[a-zA-Z]' then left(str, 1) else '' end)) as chars
from t
union all
select str, left(rest, 1) as c, stuff(rest, 1, 1, '') as rest, lev + 1,
convert(varchar(max), (case when left(rest, 1) like '[a-zA-Z]' then chars + left(rest, 1) else chars end))
from cte
where rest > '' and len(chars) < 3
)
select str, max(chars)
from cte
where len(chars) <= 3
group by str;
Here is a db<>fiddle.

Answer 2

This might help
DECLARE #VAR VARCHAR(100)= 'sa,1235JSKL', #RESULT VARCHAR(MAX)=''
SELECT #RESULT = #RESULT+
CASE WHEN RESULT LIKE '[a-zA-Z]' THEN RESULT ELSE '' END
FROM (
SELECT NUMBER, SUBSTRING(#VAR,NUMBER,1) AS RESULT
FROM MASTER..spt_values
WHERE TYPE = 'P' AND NUMBER BETWEEN 1 AND LEN(#VAR)
)A
ORDER BY NUMBER
SELECT SUBSTRING(#RESULT,1,3)
If you want to apply this on a Tables column, you need to create Scalar function with same logic. You can find more number of articles how to create the scalar function by Googling..

Answer 3

You can use this function which is written by G Mastros to do this.
Create Function [dbo].[RemoveNonAlphaCharacters](#Temp nvarchar(MAX))
Returns nvarchar(MAX)
AS
Begin
Declare #KeepValues as nvarchar(MAX)
Set #KeepValues = '%[^a-z]%'
While PatIndex(#KeepValues, #Temp) > 0
Set #Temp = Stuff(#Temp, PatIndex(#KeepValues, #Temp), 1, '')
Return #Temp
End
Then simply call the fuction like this
SELECT LEFT(dbo.RemoveNonAlphaCharacters(colName), 3)
FROM TableName
Reference: G Mastros answer on "How to strip all non-alphabetic characters from string in SQL Server" question.

Answer 4

Well, this is ugly, but you could replace all the characters you don't like.
In your example, this would be:
SELECT REPLACE (REPLACE (REPLACE (REPLACE ('sa,123k', '1', ''), '2', ''), '3', ''), ',', '')
Obviously, this needs a lot of replaces if you need all numbers and other sorts of characters replaced.
Edited, based on your comment:
SELECT REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE (REPLACE ('123456gh,.!879k', '1', ''), '2', ''), '3', ''), ',', ''), '4', ''), '5', ''), '6', ''), '.', ''), '!', ''), '7', ''), '8', ''), '9', '')